1. Field of the Invention
The present invention relates to a projector and drive control of a light source lamp included in the projector.
2. Description of the Related Art
Projectors have been used widely to project an expanded image on a screen. The projectors are used under various conditions on the lightness of working environment, the focal length of a projection lens, and the projection distance. A number of techniques have been proposed to regulate the brightness and the contrast ratio of a projected image according to these parameters for the good viewability of the projected image.
For example, a technique disclosed in Japanese Patent Laid-Open Gazette No. 8-23501 drives a zoom mechanism of a projection lens according to the luminance of a screen and varies the size of a projected image to regulate the brightness and the contrast ratio of the projected image.
A technique disclosed in Japanese Patent Laid-Open Gazette No. 11-69264 regulates the brightness and the contrast ratio of a projected image according to the zoom ratio of a projection lens.
A technique disclosed in Japanese Patent Laid-Open Gazette No. 2002-300498 controls the voltage of a light source lamp and the contrast of an input video signal according to the lightness of a room, the projection distance, the screen size, and the intensity of the input video signal to project an image of the optimum brightness on the screen.
Light source lamps included in multiple projectors of an identical model generally have slightly different performances. For example, there is a variation in luminance of illumination light emitted by the light source lamps driven with a preset driving power (lamp power). The light source lamp in one projector naturally deteriorates with time and decreases the luminance of illumination light. There is accordingly a variation in luminance of illumination light emitted by the light source lamp driven with a fixed lamp power. This leads to variations of the brightness and the contrast ratio of a resulting projected image. No techniques have been proposed to take into account such a difference among the performances of the light source lamps included in multiple projectors of an identical model or a deteriorating performance of the light source lamp in one projector.